This invention relates to an electrical connector having a noise-proof metal shell, and more particularly to an electrical connector having an improved connection between a noise-proof metal shell and a grounding element to be connected to a ground.
A connector having at contacts 1 a metal shell 2 for preventing inductive interference as shown in FIG. 1 has been used as a so-called "interface connector" for connecting a printed circuit board and an input circuit in a so-called office automation appliance such as a personal computer.
Such a connector generally includes the desired number of the contacts 1 having L-shaped contact tails 1a and fixed in an L-shaped insulating block 3, and hexagonal studs 4 threadedly engaging connecting pieces 5a of L-shaped grounding elements 5 to embrace a mounting flange 2a of the metal shell 2 and connecting pieces 3a of the insulating block 3. In using the connector, it is fixed to a printed circuit board 6 in the following manner.
First, the contact tails 1a of the contacts 1 are inserted into soldering apertures 7 formed in a circuited pattern 6a of the printed circuit board 6 as shown in FIG. 1. Thereafter, fixing pieces 5b of the grounding elements 5 and the printed circuit board 6 together with a fixing piece 3b of the insulating block 3 are clamped by means of set screws 8 and nuts 9 so that these members are embraced by the nuts 9 and heads of the set screws. In this manner, the metal shell 2 is connected to the ground pattern 6b of the printed circuit board 6 for use.
Moreover, each hexagonal stud 4 is often formed with an internal thread (not shown) in an end which is not connected to the grounding element 5. The internal threads of the hexagonal studs 4 are adapted to threadedly engage screw thread members (not shown) rotatably provided on a mating connector (not shown) so that the hexagonal studs 4 are frequently used as part of locking means for preventing dislodgment of these connectors.
With this connector of the prior art, the metal shell 2 is readily removed from the connector by loosening the hexagonal studs 4 so that it is very convenient for maintenance, inspection and cleaning for the contacts 1. In case of being used under a condition prone to vibration, however, there is a risk of the hexagonal studs 4 being loosened during use. Moreover, a plastic material of the insulating block 3 may shrink due to aging to loosen the tightness of the hexagonal studs 4. Therefore, connection between the metal shell 2 and the grounding elements 5 for grounding the metal shell 2 may become faulty with the result that the noise preventing effect is reduced and the reliability in operation is lost.
Instead of the locking means of the threaded engaging hexagonal studs 4 as shown in FIGS. 1 and 2, another means may be used for preventing dislodgment of the connector. In this case, a metal shell of a connector is provided with locking members formed with openings in which hook pieces fixed to a mating connector are latched. In this case, the locking members may be formed by extending the mounting flange 2a outwardly of hexagonal studs 4 or by providing an additional member constituting the locking members. In any case, such a construction will provide a longer connector which does not fulfill the requirement of miniaturization of connectors with the recent tendency of electronic appliances to be miniaturized.
In case of using the hexagonal studs 4, moreover, arranging and tightening steps of the screw members are required which make difficult automatic assembling of connectors and do not meet the requirement to reduce the number of parts.